<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    * {
        margin: 0;
        padding: 0;
    }

    #header,
    #footer {
        width: 100%;
        background-color: #333;
    }

    #content {
        width: 100%;
        box-sizing: border-box;
        padding-left: 200px;
        padding-right: 200px;
    }

    .clearfix:after,
    .clearfix:before {
        content: "";
        display: table;
        clear: both;
    }

    .fl {
        float: left;
    }

    #content .center {
        width: 100%;
        height: 200px;
        background: aqua;
      
    }

    #content .left {
        width: 200px;
        height: 200px;
        position: relative;
        margin-left: -100%;
        right: 200px;
        background: blue;
      
    }

    #content .right {
        width: 200px;
        height: 200px;
        margin-right: -200px;
        background:green;
    
    }
</style>

<body>
    <header id="header">header</header>
    <section id="content" class="clearfix">
        <div class="center fl">center</div>
        <div class="left fl">left</div>
        <div class="right fl">right</div>
    </section>
    <footer id="footer">footer</footer>
</body>

</html>